1. Field of the Invention
The present invention relates to a fluid disinfection unit. More particularly, the present invention relates to a modular water disinfection unit which employs ultraviolet radiation to inactivate microorganisms.
2. Description of the Prior Art
It is known that irradiation of a fluid, such as water, with ultraviolet light will disinfect the water through inactivation of microorganisms therein, provided the irradiation intensity and exposure duration are above a minimum "dose" level (often measured in units of microwatt seconds per square centimeter). Ultraviolet water disinfection units, such as those commercially available from Trojan Technologies Inc. under the tradename UV600, employ this principle to disinfect water for human consumption. Generally, water to be disinfected passes through a pressurized stainless steel cylinder which is flooded with ultraviolet radiation. Large scale municipal wastewater treatment equipment, such as that commercially available from Trojan Technologies Inc. under the tradename UV3000, employ this same principle to disinfect treated wastewater. Specifically, ultraviolet radiation emitting lamps are submerged in an open channel wherein the wastewater is exposed to radiation as it flows past the lamps. For further disclosure of fluid purification systems employing ultraviolet radiation see U.S. Pat. Nos. 4,482,809, 4,872,980 and 5,006,244 and copending U.S. patent application Ser. No. 08/026,572, the contents of each of which is incorporated herein by reference.
Residential ultraviolet water disinfection products can vary in exact construction from one manufacturer to the next while still achieving similar operational characteristics. The major components that are common to most or all residential ultraviolet water disinfection units include: an ultraviolet radiation lamp; a water cylinder (often constructed of stainless steel because of the inherent resistance to corrosion and ultraviolet radiation); fastening fixtures/devices to secure the lamp in the cylinder; sealing devices to prevent water leakage from the entry point(s) of the lamp; a lamp ballast (power supply and starter); and power cords to connect the lamp to the ballast and to connect the ballast to external power. In addition, many residential ultraviolet disinfection products also contain the following components: a quartz sleeve with a larger diameter than the ultraviolet radiation lamp, which encases and thus protects the ultraviolet radiation lamp; an electrical circuit or printed circuit board which is capable of monitoring the lamp operation, monitoring signal(s) from an ultraviolet radiation intensity sensor built into the cylinder, and/or triggering alarms within the residence if the monitored signals indicate incorrect operation.
A problem associated with prior art residential ultraviolet water disinfection units is the difficulty in interchanging, servicing, and replacing electrical component parts. Residential ultraviolet water disinfection units presently available use soldered or crimped electrical connections between the lamp connector, ballast, electrical circuits (or printed circuit boards) and the power cord. Removal or replacement of defective, damaged or worn out electrical components requires special tools such as soldering and crimping equipment and, in many cases, may require wiring preparation and installation that cannot reliably be undertaken by the end user.
Another problem that occurs intermittently with certain residential ultraviolet water disinfection units involves interference in the light (radiation) path between the lamp and ultraviolet sensor by wires on the outside of the lamp. In order to clearly understand this problem, further background explanation is required.
Commercially, the most popular ultraviolet radiation lamp constructions for use in North American residential water disinfection units are the preheat and instant start styles that have all external electrical connections moved to one end of the lamp. With all electrical connections at one end, the user only needs to attach one connector to power the lamp. The single-ended preheat construction has a four-wire connection at one end, while the instant start lamp has a two-wire connection at one end. A powered filament is required at each end for the lamp are, so one or two Teflon-insulated wires are run along the outside of the lamp to connect the lamp end that has the external electrical connections to the filament at the other end. Residential water disinfection units that feature ultraviolet-radiation sensitive sensors to monitor the radiation intensity level rely on there being an optical path between the lamp and the sensor that is unblocked, save for the water that is being disinfected. If the angular orientation of Teflon-insulated wires is not specifically controlled by the design of the lamp, cylinder and securing fixtures, the wire insulation may block a portion of the ultraviolet radiation measured by the sensor, and cause a low (inaccurate) intensity feedback signal from the sensor. A low intensity feedback signal may prompt the end user to seek or perform unnecessary servicing.
Another problem that can exist with residential ultraviolet disinfection is that of "shadowing" caused by the lamp (or lamp and sleeve) support fixtures. When ultraviolet radiation lamps that have all external electrical connections at one end are employed for disinfection in a closed and pressurized cylinder, it is cost-effective to have the lamp enter the cylinder or one end only and to employ a support clip or fixture inside the other end of the cylinder to support the end of the lamp that does not have the external electrical connections (typically a closed end). The support clip or fixture must provide mechanical support and center positioning of the lamp or, if present, the protective sleeve surrounding the lamp. The support clip or fixture must provide centering for insertion of a replaced lamp or, if present, the protective sleeve so that an unskilled individual who is inserting the lamp from the one open end of the reactor chamber (cylinder) can simply push the lamp into place and have it automatically locate a centered position, regardless of the orientation of the reactor chamber or whether the lamp axis is ideally parallel to the reactor chamber axis when the lamp end reaches the fixture. The problem that exists with such a support fixture is that in order for it to be cost-effective and yet provide all of the mechanical features named, it can be bulky and can tend to block direct ultraviolet radiation from reaching the interior surfaces in the closed end of the cylinder. This blocking effect is commonly referred to as "shadowing" and is undesirable because any area under shadow will receive less of the ultraviolet radiation intended for disinfection of the water.
It would be desirable to have a fluid disinfection unit which, from the perspective of the end user, is free of relatively complicated electrical connections and/or exhibits minimal or no "shadowing".